A rotor such as this for a steam turbine is known, for example, from EP 0 991 850 B1, extends along a rotation axis, and comprises at least two rotor parts which are adjacent to one another in the axial direction. In this case, the two rotor parts are welded to one another on mutually facing axial end faces by means of a circumferential, annular weld zone which is closed in the circumferential direction. A cooling channel system is formed in the rotor and has at least one inlet flow channel, at least one outlet flow channel and a cooling channel. The cooling channel carries cooling steam from at least one inlet flow channel to the at least one outlet flow channel. The at least one inlet flow channel taps off the cooling steam from the working steam at a position on the rotor surface, and supplies it to the cooling channel. In contrast to this, the at least one outlet flow channel taps off the cooling steam from the cooling channel and passes this to or through a cooling zone in the rotor. A pressure difference can be formed between the inlet and the outlet of the cooling channel system by suitable positioning of the at least one inlet flow channel and of the at least one outlet flow channel, and this pressure difference is sufficient to pass the cooling steam from the at least one steam tapping point to the at least one cooling zone without any additional measures.
In the case of the known rotor, the cooling channel extends concentrically about the rotation axis. The inlet flow channels are arranged in the area of a diffuser of a single-flow high-pressure turbine, while the outlet flow channels are positioned in the center of a two-flow medium-pressure turbine. The cooling channel in this case extends within the common rotor which is provided for the high-pressure turbine and for the medium-pressure turbine. This rotor is mounted axially between the high-pressure turbine and the medium-pressure turbine. The cooling line accordingly also extends centrally through this bearing. This means that this bearing is subject to an increased temperature load, so that additional measures are required for protection of this bearing.
The known rotor is designed on a so-called “drun principle”, that is to say the rotor is formed from a number of “drums”. A drum such as this is a cylindrical or truncated conical solid body which, in principle, may contain cavities, such as channels and chambers, for a cooling system. A rotor of a drum design is generally characterized by a small number of drums, which are preferably of different design. In this case, each drum is associated with a number of turbine stages. The end faces of adjacent drums generally rest on one another over their complete area.
DE 196 20 828 C1 discloses an integral rotor which is arranged in a two-flow steam turbine and likewise contains a cooling channel system. A cavity is formed in the center of the hot steam supply on the casing in this rotor and is closed again with the aid of a cover, with the cover at the same time carrying out a flow guidance function. An axial cooling channel originates from each of two axially opposite sides of this cavity. One cooling channel communicates with an inlet flow channel which takes the cooling steam from a pressure stage of one flow. In contrast to this, the other cooling channel communicates with an outlet flow channel, which supplies the cooling steam to a pressure stage of the other flow. The complexity for providing this internal cooling is comparatively high, since, in order to produce the cooling channels, the cavity must first of all be formed on the circumference of the rotor, and must then be closed again. A further disadvantageous feature in this case is that the chosen positioning of the cavity precisely at that point on the rotor which is subject to the highest thermal loads and to high mechanical loads during operation of the steam turbine results in weakening of the structure. Furthermore, additional complexity is required in order to close the cavity again by means of the corresponding cover.
EP 0 761 929 A1 discloses a rotor for a gas turbine, on which a compressor part, a central part and a turbine part are formed and which is composed predominantly of individual rotating bodies which are welded to one another and whose geometric shape leads to the formation of axially symmetrical cavities between the respectively adjacent rotating bodies. In this rotor, a further, cylindrical cavity, which extends about the center axis of the rotor and extends from the downstream end of the rotor to the final upstream cavity, as well as at least two tubes are provided, which have different diameters and different lengths, at least partially overlap telescopically and are arranged in the cylindrical cavity. The tubes are each firmly anchored at a fixing point, with the fixing points for the tubes being located at axially different points. The tubes are each provided with at least two aperture openings in the casing, with at least one opening being arranged in the turbine part and at least one opening being arranged in the compressor or central part. The openings in the various tubes overlap in the operating state in the turbine part, and overlap in the cold state in the compressor and center part. This means that the rotor can be heated up more quickly when the turbine is being started up, while cooling is provided in the operating state. Compressed air is in this case tapped off from a suitable compressor stage for preheating and for cooling, and is supplied axially to one of the tubes.
This known rotor is based on the so-called “disk principle”, that is to say the rotor is formed from a number of “disks”. The disks correspond to bodies that are in the form of disks and, radially on the outside, have an axially projecting edge area which may be in the form of a sleeve. The edge areas of the adjacent disks rest on one another along relatively small annular surfaces. These disks are therefore the rotating bodies mentioned above. In contrast to a drum, each disk is associated with only a small number of turbine stages, in particular in each case with only a single turbine stage. In a corresponding manner, a rotor based on a disk design comprises a comparatively large number of disks which, furthermore, are preferably physically identical. The cavities which are produced in a rotor based on the disk principle are used predominantly to reduce the inertia forces, but may also be used for a cooling system.
Further rotors for gas turbines which are based on this disk principle can be found, for example, in DE 854 445 B, DE 198 52 604 A1 and DE 196 17 539 A1.